Fig. 6

Diesel exhaust PAH mixtures alter Treg differentiation and have AHR and CYP dependent effects on Th17 differentiation. Naïve CD4⁺ T cells were isolated from WT (C57BL/6 J), Ahr^−/−, or CypTKO mice. At time 0 cells were exposed to a dose-response (8 doses) of SRM1650b PAH mixtures, SRM2975 PAH mixtures, or solvent control and cultured for 3 days. a Representative flow plots of WT Treg differentiation at 0.00001 μg/mL OC, measured by percent FOXP3 positive cells. b SRM2975 PAH mixtures suppressed Treg differentiation at the lowest dose compared to solvent control. c Representative flow plots of WT (left), Ahr^−/− (middle), and CypTKO (right) at 5 μg/ml OC. d SRM1650b PAH mixtures enhanced Th17 differentiation at 40 μg/ml OC (top) and SRM2975 PAH mixtures had no effect (bottom). e In Ahr^−/− cells, SRM1650b (top) and SRM2975 (bottom) PAH mixtures had no effect on percent IL-17 positive cells. f In CypTKO cells, SRM1650b PAH mixtures enhanced Th17 differentiation at 5μg/ml OC (top) and SRM2975 PAH mixtures enhanced Th17 differentiation at the three highest doses (bottom). Results are mean ± SEM of n = 2 (WT Treg), n = 7 (WT Th17), n = 4 (Ahr^−/− Th17), and n = 6 (CypTKO Th17). Significant differences among groups (p < 0.05) are indicated by an asterisk. Abbreviations: AHR, aryl hydrocarbon receptor; CYP, cytochrome P450; TKO, triple knockout; SRM, standard reference materials; PAH, polycyclic aromatic hydrocarbons; OC, organic carbon